1. Field of the Invention
The present invention relates to radar systems for detecting threats in accordance with stored beam parameters of signal emitters associated with the threats and, more particularly, to a radar system for detecting threats in accordance with adaptively redefined stored beam parameters associated with the threats. In other aspects the present invention relates to radar systems for tracking signals, and more particularly, to radar systems which verify that tracking has not been transferred to a second signal having parameters which are similar to the original signal.
2. Description of the Prior Art
As is known in the radar art, devices which employ active radar systems necessarily contain signal emitters whose emitted signals, commonly known as beams and so referred to herein, may be used to identify the device after the characteristic parameters of the emitted signals, or beams, have been established and associated with the device. That is, devices which employ active radar systems contain at least one signal emitter which can be used to identify the device after the characteristic beam parameters for the emitter are determined and have been associated with the particular device. In the military sciences, devices which employ active radar systems include offensive and defensive weapons as well as their delivery vehicles. Although such weapons and their delivery vehicles are often used in a defensive posture, the presence of a weapon or a delivery vehicle is considered to be a threat to the successful mission and/or survival of the opposing military force so that all such military devices employing active radar systems are, quite properly, designated as threats by the opposing force. Therefore, according to the general experience of the radar art as applied to use in the military sciences, it is well known in the prior art that military threats containing active radar systems may be detected in accordance with at least one beam which has a known association with the threat.
In the prior art, threat detection systems have detected threats by detecting the presence of beams which have characteristic parameters and comparing these detected beams to stored beams having similar characteristic parameters and which are known to be associated in various combinations with particular threats. The associations of the stored beams with a particular threat are cataloged as a stored threat so that when the comparison of the detected beams and the stored beams indicates the presence of one or more detected beams substantially similar to one or more stored beams that are cataloged as a stored threat the threat detection system indicates the presence of a detected threat. Although these prior art systems are adequate to detect threats whose actual beam parameters correspond to the stored beam parameters associated with the threat, the prior art systems are unable to adaptively redefine their stored beam parameters in response to detected beams which exhibit parameters that are different than those of the stored beams previously associated with the threat. Therefore, it has been possible for a threat to confuse prior art threat detection systems, or to avoid detection altogether by causing the emitters of its radar system to exhibit beam parameters deviating from the predetermined, or stored, beam parameters previously associated with the and cataloged as a stored threat. Although some prior art threat detection systems afford the flexibility that their stored beam parameters and stored threat signals may be altered so that their stored beams may be redefined and associated with new stored threats once the deviations of the actual beam parameters and their respective threat associations have become known, it remains for some external intelligence gathering operation to ascertain the appropriate stored beam parameters and associate these different stored beams with the appropriate stored threats. For any radar system which detects devices employing active radars, the time necessary to perform this intelligence gathering operation is inconvenient and, for threat detection systems engaged in military conflicts, this delay could be fatal to the success of the mission. Moreover, it is unlikely that every combination of actual beam parameters for each particular threat that will be encountered will be available as a stored beam parameter of a stored threat. Therefore, there was a need in prior art threat detection systems for a capability to adaptively redefine the parameters of stored beams which are associated with a particular stored threat, and adapt the system's stored threats in accordance therewith.
Prior art radar systems have been developed for tracking the incidence of threat signals upon an antenna that is sensitive to microwave energy. Some of these systems are capable of detecting a situation in which the radar system has lost track of a threat signal. However, for the situation in which a second signal having similar paramters is substituted for the signal which was originally being tracked, these prior art radar sytems could confuse the second signal with the original signal and begin to track the second signal as though it were the original. There was, therefore, a need for a radar system which would not only track signals but would also be able to detect a situation in which a signal having parameters similar to the parameters of the originally tracked signal had been substituted for the original signal in the course of operation of the radar system.